A friction reduction method for dry friction surface texture based on compressive stress distribution optimization

Abstract

The invention discloses a dry friction surface texturing friction reduction method based on compressive stress distribution optimization, comprising the following steps: S1: texture patterns of different densities on the surface of a material to conduct friction and wear tests, and respectively detect the friction coefficient of the patterns to determine the texture density with the minimum friction coefficient; S2: on the basis of determining the texture density, taking the minimum standard deviation of the compressive stress as the optimization target, optimizing the texture pattern, so that under the optimized texture scheme, the compressive stress is maximized and concentrated at the lowest point of the friction coefficient, thereby obtaining the optimal texture scheme; S3: weaving the optimized pattern on the surface of the material according to the texture density obtained in step S1; the invention optimizes the compressive stress distribution by optimizing the texture pattern to make the compressive stress distribution more uniform after determining a relatively reasonable texture density, thereby obtaining a texture scheme with a smaller friction coefficient; a scheme with a relatively smaller friction coefficient is obtained by optimizing calculation, thereby saving time and material costs.

Description

Technical Field

[0001] The invention belongs to the field of material technology, and in particular relates to a dry friction surface texture reduction method based on compressive stress distribution optimization. Background Art

[0002] Laser surface texturing technology is to manufacture a microstructure array with a specific shape, arrangement and size on the surface without changing the material itself to obtain the required friction and wear performance. Research in recent years generally believes that texture shape has a significant effect on the friction reduction effect. However, current research on texture shape is mainly focused on the comparison of various groove shapes to obtain the best texture shape, and research on texture shape optimization is mainly focused on the dynamic pressure distribution of lubricating fluid under lubrication conditions as a variable. There is still a lack of explanation of the principle of improving friction performance under dry friction conditions and optimization methods. Summary of the invention

[0003] The purpose of the present invention is to provide a dry friction surface texturing friction reduction method based on compressive stress distribution optimization to solve the problems raised by the above background technology.

[0004] To achieve the above object, the present invention provides the following technical solution: a dry friction surface texture reduction method based on compressive stress distribution optimization, comprising the following steps:

[0005] S1: Texture patterns of different densities on the surface of the material to conduct friction and wear tests, and test the friction coefficients of the patterns to determine the texture density with the minimum friction coefficient;

[0006] S2: On the basis of determining the texture density, the texture pattern is optimized with the minimum standard deviation of compressive stress as the optimization target, so that under the optimized texture scheme, the compressive stress is maximized and concentrated at the lowest point of friction coefficient, thereby obtaining the optimal texture scheme;

[0007] S3: Texture the optimized pattern on the material surface according to the texture density obtained in step S1.

[0008] Preferably, in step S1, the texture pattern used for the friction and wear test is a circular pattern.

[0009] According to existing research, the circular texture shape itself has a small friction coefficient, and the circular pattern structure is simple, which facilitates subsequent optimization.

[0010] Preferably, in step S2, when optimizing the texture pattern, an isogeometric topology optimization method is used. First, a plurality of circumferentially uniformly distributed feature points are set on the texture pattern with the center of the texture pattern as the origin, and the feature points are marked as ,in, is the marking number of the feature points, and then the feature points are connected by B-spline curves. The internal area of ​​the closed pattern connected by the B-spline curve is marked as , other areas are marked as , at this time, the calculation formula of the compressive stress standard deviation is:

[0011] , where for The standard deviation of the compressive stress in the region, For feature points The compressive stress value, is the average compressive stress, is the total number of nodes in the calculation of compressive stress; then the closed pattern connected by the B-spline curve is optimized using the COMSO finite element software, and the mathematical expression of the optimization process is: , where is a constant whose value is , is the texture density, is the optimized boundary shape, for The area of ​​the region, for The area of ​​the region.

[0012] Preferably, in step S3, laser surface texturing technology is used when texturing patterns on the material surface.

[0013] Laser surface texturing technology is mature and has good texturing effects.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] The present invention optimizes the compressive stress distribution by optimizing the texture pattern to make the compressive stress distribution more uniform after determining a relatively reasonable texture density, thereby obtaining a texture solution with a smaller friction coefficient; the solution with a relatively small friction coefficient is obtained by optimizing the calculation, which can save time and material costs for experimental exploration. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a line graph of the friction coefficient of the texture pattern provided by the embodiment of the present invention at different texture densities;

[0017] Figure 2 is a line graph of the friction coefficient of the material surface provided by the embodiment of the present invention when it is subjected to different pressures without a textured pattern;

[0018] Figure 3 is a schematic diagram of optimized pattern feature points and regions provided by an embodiment of the present invention;

[0019] Figure 4 is a compressive stress distribution diagram of an initial circular pattern provided by an embodiment of the present invention;

[0020] Figure 5 is an optimized pattern compressive stress distribution diagram provided by an embodiment of the present invention;

[0021] Figure 6 It is a line graph of friction coefficient under different texture schemes provided in the embodiments of the present invention. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] See also Figure 1-Figure 6 The present invention provides a technical solution: a dry friction surface texturing and friction reduction method based on compressive stress distribution optimization. In this embodiment, SA508.Gr3.Cl2 material is used for dry friction surface texturing and friction reduction, and the steps are as follows:

[0024] S1: Circular patterns of different densities are textured on the surface of the material to conduct friction and wear tests, and the friction coefficient of the patterns is tested respectively. The obtained friction coefficient curve is as follows: Figure 1 As shown; According to the test results, the friction coefficients of different texture densities are lower than those of the surface without texture, and the friction coefficient shows a trend of first decreasing, then increasing, and then decreasing as the texture density increases;

[0025] Then the material was subjected to friction and wear tests under different loads. As the load increased, the average friction coefficient of SA508.Gr3.Cl2 and the friction coefficient curve were as follows: Figure 2 As shown; according to the test results, as the load increases, the friction coefficient of SA508.Gr3.Cl2 first decreases, then increases, and then decreases. The change of its friction coefficient with increasing load has a certain similarity with the change of the friction coefficient texture density increase; it is inferred that the surface texture changes the size and distribution of the compressive stress, and different compressive stress sizes and distributions affect the overall friction coefficient. Therefore, the reason why the surface texture reduces the friction coefficient is that the surface texture changes the compressive stress distribution. By using surface texture to evenly distribute the surface compressive stress in the area with the lowest friction coefficient, the lowest friction coefficient can be achieved.

[0026] S2: According to Figure 1Determine the texture density corresponding to the lowest friction coefficient. Since there is no clear quantitative relationship between the friction coefficient and the compressive stress between materials, determining the relationship requires a lot of experimental research. Therefore, the present invention proposes a relatively simple optimization method. According to experience, a slight change in pressure will not produce a sharp increase in the friction coefficient. Therefore, when the experiment finds the texture density with the lowest friction coefficient, the compressive stress under this texture density is distributed around the lowest point of the friction coefficient. On this basis, the texture pattern is optimized with the lowest standard deviation of the compressive stress as the optimization goal, so that under the optimized texture scheme, the compressive stress is maximized and concentrated at the lowest point of the friction coefficient, and the optimal texture scheme can be obtained.

[0027] Since the slight change of the pattern edge has little effect on the texture pattern, and the optimization calculation amount is very large to optimize the position of each point on the pattern edge, it is very difficult to achieve optimization; therefore, the present invention uses the isogeometric topology optimization method to optimize the texture pattern. In this embodiment, 8 feature points are determined in the circular pattern, which are marked as ,in, is the marking number of the feature point. The feature point is determined by taking the center of the circular pattern as the origin, eight polar coordinate angles (0°, 45°, 90°, 135°, 180°, 225°, 270°, 315°) and the polar coordinate radius Determine and connect the feature points through B-spline curves to obtain the corresponding closed pattern, and the amount of calculation is relatively small.

[0028] During the optimization process, the internal area of ​​the closed pattern connected by the B-spline curve is marked as , other areas are marked as (like Figure 3 As shown), in this embodiment, the polar coordinate radius of the selected 8 feature points is 0.1 mm. At this time, the calculation formula for the compressive stress standard deviation is: , where for The standard deviation of the compressive stress in the region, For feature points The compressive stress value, is the average compressive stress, is the total number of nodes in the calculation of compressive stress; then the closed pattern connected by the B-spline curve is optimized using the COMSO finite element software, and the mathematical expression of the optimization process is: , where is a constant whose value is , is the texture density, is the optimized boundary shape, for The area of ​​the region, for The area of ​​the region.

[0029] Finally, the contact pressure distribution of the contact surface before and after optimization is obtained as follows: Figure 4 and Figure 5 As shown in Figure 2, the standard deviation of compressive stress before optimization is 1.35×10 7 Pa, the standard deviation of the optimized compressive stress is 1.26×10 7 Pa.

[0030] Finally, the optimized pattern, circular pattern and untextured surface were subjected to friction and wear tests. In this embodiment, the friction and wear test was a ball-disc test, and both the grinding ball and the disc were made of SA508.Gr3.CL2 material. During the test, the load applied to the ball was 5N, the friction radius was 4mm, and the disc rotated at a speed of 112r / min. After conversion, the linear speed of the ball was 47mm / s. Test results (such as Figure 6 ), according to the test results, the optimized pattern has the lowest friction coefficient. The average friction coefficient and wear rate of the optimized pattern under different conditions are shown in Table 1:

[0031] Table 1 Average friction coefficient and wear rate of different texture schemes

[0032]

[0033] Finally, the optimized pattern is textured on the material surface according to the texture density obtained in step S1 by laser surface texturing technology, so that SA508.Gr3.CL2 material with a low surface friction coefficient can be obtained.

[0034] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A dry friction surface texture reduction method based on compressive stress distribution optimization, characterized in that: The following steps are involved: S1: Circular patterns with different densities are textured on the surface of the material to conduct friction and wear tests, and the friction coefficients of the patterns are tested to determine the texture density with the minimum friction coefficient; S2: On the basis of determining the texture density, the texture pattern is optimized with the minimum standard deviation of compressive stress as the optimization goal, so that under the optimized texture scheme, the compressive stress is maximized and concentrated at the lowest point of the friction coefficient, thereby obtaining the optimal texture scheme. Specifically, the isogeometric topology optimization method is used when optimizing the texture pattern. First, a plurality of circumferentially uniformly distributed feature points are set on the texture pattern with the center of the texture pattern as the origin, and the feature points are marked as ρ i (i=1,2,3…), where i is the mark number of the feature point, and then the feature points are connected by B-spline curves, and the internal area of ​​the closed pattern connected by the B-spline curve is marked as Ω B , the other regions are marked as Ω A , at this time, the calculation formula of the compressive stress standard deviation is: In the formula, J(Ω A ) is Ω A Standard deviation of regional compressive stress, P i is the compressive stress value of characteristic point i, P A is the average value of compressive stress, and n is the total number of nodes when calculating compressive stress; then the closed pattern connected by the B-spline curve is optimized using the COMSO finite element software, and the mathematical expression of the optimization process is: In the formula, c is a constant, and its value is ε is the texture density, u out is the optimized boundary shape, Ω A The area of ​​the region, Ω B The area of ​​the region; S3: Texture the optimized pattern on the material surface according to the texture density obtained in step S1.

2. The dry friction surface texture reduction method based on compressive stress distribution optimization according to claim 1 is characterized in that: In step S3, laser surface texturing technology is used to texture patterns on the material surface.

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